Catalytic converters are widely used in motor vehicle exhaust systems to reduce the toxicity of emissions. In a typical catalytic converter, a substrate takes the form of a porous structure that is coated with catalytic materials. The porous structure is often a ceramic that has been extruded through a die such that a large number of parallel flow channels (cells) are formed. The exhaust gas is expelled by the engine at velocity and is routed to the catalytic converter through an exhaust pipe. The catalytic converter is typically placed in a metal can having a diameter larger than that of the exhaust pipe which is connected to the remainder of the exhaust system by sections of flared pipe called inlet and outlet diffusers.
The interposition of a catalytic converter into the exhaust system can impede gas flow, creating backpressure that can significantly reduce engine power and increase fuel consumption.